Method and apparatus for cutting sheet material

ABSTRACT

A method and apparatus for cutting pattern pieces from an anisotropic sheet material having different cutting characteristics along different principal directions utilize a small cutting wheel that is guided along the periphery of a pattern piece to be cut by means of a digital control computer. The computer derives command signals from a stored cutting program and applies the signals to drive motors within a tool carriage to cause the cutting wheel to move along the periphery of the pattern piece. A load control mechanism is utilized to support the cutting wheel from the tool carriage and to vary the force with which the wheel is urged or pressed into cutting contact with the sheet material. When the wheel moves in cutting engagement with the material in a direction that offers increased resistance to cutting, the load control mechanism presses the cutting wheel more firmly against the material and when the wheel moves in a direction of reduced cutting resistance, the load control mechanism partially unloads the wheel to prevent cutting or increased wear of the work surface on which the sheet material is supported.

[451 Nov. 20, 1973 United States Patent [191 Pavone et al.

[ METHOD AND APPARATUS FOR CUTTING [57] ABSTRACT A method and apparatusfor cutting pattern pieces from an anisotropic sheet material havingdifferent cutting characteristics along different principal directionsutilize a small cutting wheel that is guided along the periphery of apattern piece to be cut by means of SHEET MATERIAL [75] Inventors:Robert J. P

avone, Wapping; Leonard R. Lenders, South Windsor, both of Conn.

[73] Assignee: The Gerber Scientific Instrument Company, South Windsor,Conn.

d e e e ea m mnimm m mm m m h m 0 mm til wuw m m mm ad a digital controlcomputer. The computer deriv command signals from a stored cuttingprogram an applies the signals to drive motors withi riage to cause thecutting wheel to move riphery of the pattern piece. A load c nism isutilized to support the cutting w tool carriage and to vary the forcewith which the wheel is urged or pressed into cutting contact wit sheetmaterial. When the wheel moves in cutting engagement with the materialin a dire z ucm 2 8 7 7 "4 9 3 u I 1 m8 m "M 7 m mm 1 1 u m n m 1 m m J2 n a u m we M u L "f C d m d w Dl S at all a nel- F A U IF ll l l] 2 l.2 0o 2 2 5 55 increased resistance to cutting, the loa [56] ReferencesCited UNITED STATES PATENTS anism presses the cutting wheel more firmlyagainst the material and when the wheel moves in a direction of reducedcutting resistance, the load control mechanism p 83/12 artially unloadsthe wheel to prevent cutting or 83/12 X increased wear of the worksurface on which the sheet material is supported.

3,522,753 8/1970 Schmied 3,537,345 11/1970 Luppino........ 3,673,9007/1972 Primary ExaminerJ. M. Meister Attorney-John C. Linderman 25Claims, 6 Drawing Figures METHOD AND APPARATUS FOR CUTTING SHEETMATERIAL BACKGROUND OF THE INVENTION The present invention relates to amethod and apparatus for cuttingsheet material in an automated cuttingsystem. More particularly, the invention is concerned with cuttinganisotropic sheet materials such as fibrous composite tapes which havewidely divergent strengths and cutting characteristics along differentprincipal ax'esof the material.

The concept of utilizing an automatically controlled cutting tool forcutting pattern pieces from a sheet of material is already well known inthe art. US. Pat. No. 3,477,322 entitled Device for Cutting SheetMaterial" issued Nov. 1 l, 1969 to the assignee of the present inventiondiscloses a cutting system in which a control computer guides a cuttingtool over the work surface of a cutting table on which sheet material isheld in a spread condition. The movements of the cutting tool arecontrolled so that the tool moves around the periphery of one or morepattern pieces in the cutting operation.

It is also known that the cutting tool in automated cutting systems ofthe type disclosed in the .abovereferenced patent can be formed as asmall cutting wheel or disc having a diameter that is large enough topermit the wheel to cut through the sheet material during the cuttingoperation. US. Pat. application Ser. No. l l9,l5l filed Feb. 26, 1971entitled Method and Apparatus For Cutting Sheet Material" and assignedto Gerber Garment Technology, Inc. discloses a rotatably driven cuttingwheel which, under the control ofa computer or similar apparatus,translates through a sheet of material spread on a work table to performa cutting operation in a manner generally similar to the apparatus ofthe present invention.

While many sheet materials are isotropic and have generally uniformcutting properties throughout, anisotropic sheet materials havingdifferent strength characteristics or different resistances to cuttingalong different axes can pose peculiar cutting problems, particularlywhere the differences in the cutting characteristics along the principalaxes are extreme. When a pattern piece in a sheet of anisotropicmaterial is circumscribed by the cutting tool, the tool may encountereach of the extremes in cutting resistance. For example, compositematerials such as boron fiber sheet or tape produced by applying a boroncoating to a very fine tungsten wire 0.0005 inch in diameter and bindinga plurality of the fibers having a 0.008 inch diameter in closely packedrelationship on a planar base or backing such as aluminum foil are knownto have exceptional tensil and beinding strength characteristicsassociated with the principal axis aligned with the fibers. Theresistance to 1 cutting such tapes in a direction transverse to thefibers requires substantially greater cutting forces than required whencutting the material in a direction parallel to the fibers.

In carrying out such cutting operations in automatically controlledcutting systems the sheet material is usually spread on the resilientwork surface of a cutting table and the table and cutting tool are movedrelative to one another while the tool is-held in cutting engagementwiththe material. If'the cutting tool is held in engagementwith fibroussheet material at a relatively uniform detrusion force, that is a forcenormal to the plane of the sheet material, the tool can cause extensivedamage to the work surface of the cutting table as a pattern piece iscircumscribed. Asthe tool traverses a line of cut normal to the fibers,large detrusion forces may be required to cause the cutting tool topenetrate and completely sever the fibers and the backing; however, thesame detrusion forces can cause the cutting tool to penetrate too deeplythrough the sheet material and into the work surface of the cuttingtable as the tool traverses a line of cut generally parallel to thefibers due to the reduced cutting resistance and reduceed deflections ofthe bed which defines the work surface of the cutting table on which thesheet material is supported during the cutting operation. Resilient bedson the work tables are generally desirable since they allow a tool topenetrate through the sheet material by a limited amount withoutdamaging the work surface; however such beds permit greater deflectionsof the work surface and increase the difficulty of cutting anisotropicmaterials. It will be readily understood that where the sheet materialpossesses widely divergent strength characteristics in differentcoordinate directions, it may be impossible to select a single detrusionforce that would permit the cutting tool to completely penetrate thesheet material at all points along the periphery of the pattern piece tobe cut without damaging the work surface.

Accordingly, it is a general object of the present invention to disclosea method and apparatus for cutting sheet materials having differentstrength characteristics in different directions, by means of anautomatically controlled cutting tool which is urged into cuttingengagement with material by a controlled detrusion force.

SUMMARY OF THE INVENTION The present invention resides in a method andapparatus for cutting pattern pieces from anisotropic sheet materialwhich has different resistances to the cutting operation along thedifferent lines of cut through the material. The apparatus whichoperates in accordance with the method of the present inventioncomprises support means defining a work surface for holding the sheetmaterial fixedly in a spread condition as the material is moved relativeto the cutting tool in the cutting operation. Carriage means areinterposed between the support means and the cutting tool to move thesheet material and the tool relative to one another along a programmedline of cut at the periphery of a pattern piece desired from the sheetmaterial. Movement control means are connected to the carriage means forcontrolling the relative movement of the tool and the support means onwhich the sheet material is spread. Load control means connected to thecarriage means are utilized to regulate the force with which the cuttingtool is held in cutting engagement with the material at the variouspoints along the periphery of the pattern pieces. To correlate the loadsapplied through the load control means during the cutting operation withthe material characteristics, the sheet material is oriented on the worksurface with respect to a given reference direction in accordance withthe anisotropic characteristics of the sheet material. The load controlmeans then regulates the detrusion force of the tool in response to thedirection of cut produced by the movement control means.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of acutting apparatus embodying the present invention.

FIG. 2 is a side elevation view of the cutting tool and cutting table inFIG. 1 and shows the load control mechanism connected to the tool.

FIG. 3 is a front elevation view of the apparatus shown in FIG. 2.

FIG. 4 is a schematic diagram of the apparatus utilized to control thedetrusion forces applied to the cutting tool.

FIG. 5 is a plot showing the operating characteristics of the loadcontrol mechanism in one embodiment of the invention.

FIG. 6 is a plot showing the operating characteristics of the loadcontrol mechanism in another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 show anautomated cutting system for cutting anisotropic sheet material inaccordance with the present invention. The system, generally designated10, is comprised of a cutting table 12, a cutting tool 14 and a toolcarriage composed of an X carriage 16 which moves over the cutting table12 in the indicated X direction and Y carriage 18 which is mounted tothe X carriage and moves relative to the table 12 and the X carriage 16in the indicated Y direction and a control computer 20 connected to thecarriages and the tool for controlling the motions and operation of thetool during the cutting operation. The control computer 20 derivesprogram information from a memory tape 22 and develops cutting controlsignals in accordance with the information. The control signals aretransmitted through a command cable 24 to the two carriages I6 and 18 tocause the tool 14 to be translated over the table 12 in cuttingengagement with a sheet material S from which pattern pieces defined bythe tape program and shown by dotted lines are to be cut.

The sheet material S with which the present invention is concenred is ananisotropic material having different cutting characteristics along theillustrated X and Y coordinate directions of the table. An example ofsuch material would be a boron fiber sheet or tape in which the fibersare arranged in parallel, closely packed relationship and secured to abacking material such as aluminum foil as described above. Anisotropicmaterial such as the boron fiber tape having distinct directionalstrength characteristics are frequently used to form laminated articlesand, by orienting the principal axes of the tape in adjacent laminationsin different but selected directions, it is possible to build up acomposite structure with preselected strength and bendingcharacteristics. The pattern pieces such as those illustrated in FIG. 1which are to be cut from the sheet material are, therefore, laid out inaccordance with the directional characteristics of the material and thememory tape 22 is programmed accordingly.

The cutting table 12 has a frame 30 which rests on a plurality of tablelegs 32 and a bed 34 defining the work surface on which the sheetmaterial S is spread. The exposed portion of the bed 34 defining thework surface is preferably composed of a resilient material such as athick cover 36 of rubber (FIGS. 2 and 3) or similar .4 material which issufficiently resilient to allow the cutting tool 14 to be pressedthrough the sheet material S and partially into the cover 36 withoutcutting or otherwise damaging the work surface. In addition, the cover36 is provided with a plurality of small openings 38 distributed overthe entire extent of the work surface which openings communicate throughchannels 40 in the. base of the bed 34 with a vacuum pump (not shown) sothat when the sheet S is spread on the work surface it is held fixedlyin position due to the subatmospheric pressure generated at the worksurface by the vacuum pump.

The X carriage 16 is supported above the cutting table 12 on a pair ofracks 48 and 50 which extend longitudinally along the edge of the tablein the X direction and are held by brackets 52 projecting upwardly fromthe frame 30. Drive motors and pinions (not shown) within the carriage16 engage the teeth of the racks 48 and 50 to drive the carriage l6 andthe tool 14 back and forth over the table in the X direction inaccordance with the movement commands transmitted from the computer 20.

The Y carriage 18 is suspended from the X carriage 16 by means ofa guiderail 58 and a lead screw 60 that extend in the Y direction between thelateral ends of the X carriage 16. The lead screw 60 is rotated byanother drive motor (not shown) controlled from the computer 20 andthreadably engages the Y carriage 18 to position the carriage and tool14 in the Y direction over the table. Composite motions of the X and Ycarriages 16 and 18 permit the tool 14 to be translated in any givendirection over the work surface of the cutting table 12 in cuttingengagement with the sheet material to out along the periphery of apattern piece.

As seen most clearly in FIGS. 2 and 3, the cutting tool 14 is suspendedfrom the Y carriage 18 by means of a support platform 62 which extendsin cantilever fashion from an adjustable mount 64 on the projecting endof the Y carriage 18. The adjustable mount 64 is elevated or loweredwith respect to the work surface of the table 12 by a motor (not shown)controlled by the computer so that the cutting tool 14 can be broughtinto cutting engagement with the sheet material S at the beginning of acutting operation or raised out of contact with the sheet material atthe end of a cutting operation. The cutting tool 14 includes a cuttingwheel having a sharp circumferential cutting edge which cuts the sheetmaterial S when the tool is urged downwardly into engagement with thematerial by a detrusive force from the support platform 62. For cuttingrelatively hard materials such as the boron tapes, a carbide cut tingwheel such as used for cutting glass has proven to be desirable andsufficiently wear resistant to provide a useful cutting life. Thecutting wheel 70 is supported by a tool holder 72 in a quick-releasechuck 74.so that the wheel rotates freely in the holder 72 about an axis76 parallel with the work surface of the table 12 as the wheel is rolledover the work surface by the carriages l6 and 18 in cutting engagementwith the sheet material. The quick-release chuck 74 contains a borewhich receives the holder 72 in close fitting contact and a lock pin 78retains the wheel 70 and holder 72 within the chuck 74.

The wheel 70 and chuck 74 are translated with the platform 62 in part bymeans of a journaled supporting shaft 80 which provides angular rotationof the too] about the 0 axis 82 perpendicular to the work surface of thetable 12. A rotational drive motor 84 is connected to the shaft 80 bymeans of a toothed belt 86 extending between motor pulley 88 and a largeshaft pulley 90 secured to the upper end of the shaft 80. Rotationcommands are derived from the memory tape 22 by the computer 20 and areapplied to the drive motor 84 to control the angular position of thecutting wheel so that it translates tangentially along the periphery ofthe pattern piece at each point on the periphery.

ln accordance with the present invention, a load control mechanism isinterposed between the cutting tool 14 and the tool carriage 18 fromwhich it is supported for regulating the detrusive force with which thecutting tool is urged along the axis 82 into cutting engagement with thesheet material S on the work surface. The load control mechanism,generally designated 100, includes an hydraulic load cylinder assembly102 which is fixedly mounted on a small bridge 104 connected to thesupport platform 62. The load cylinder assembly 102 includes a pistonrod 106 which extends coaxially through the central bore in the shaft 80and connects through a thrust bearing 110 with the tool chuck 74. Thechuck 74 is secured rotatively to splines on the depending end of theshaft 80 by a collar 112 so that the chuck and the tool 14 rotate withthe shaft and slide axially along the shaft relative to the supportplatform 62. The thrust bearing 110 permits the chuck 74 to rotate thecutting wheel 70 about the 0 axis 82 while the detrusive force isapplied by the piston rod 106 to the cutting wheel.

The load applied to the cutting tool 70 and hence the detrusive forcewith which the cutting wheel is thrusted into the sheet material S isdetermined by the hydraulic pressure applied to the load controlcylinder assembly 102 through the hydraulic lines 114 and 116. After acutting operation, the hydraulic pressure in the lines 114 and 116 isreduced to zero and the tool 14 is lifted from the cutting table by theplatform 62 and the adjustable mount 64 when the lifting ring 120 fixedto the lower end of the shaft 80 makes contact with the collar FIG. 4 isa schematic diagram showing the controls for the load control mechanism100 and the rotational drive motor 84. The 0 command signal from thecomputer 20 is applied to a motor driver 128 which controls the outputposition of the drive motor 84 and the angular position of the cuttingwheel 70 about the 0 axis 82. The motor positions the wheel 70 so thatthe tool remains tangent to or aligned with the cutting path through thesheet material on the cutting table. The 0 command signal is alsoapplied to a signal shaper 130 which produces a dc pressure signal thatoperates a pressure modulating hydraulic valve 132. The hydraulic valveis connected to a hydraulic pump (not shown) and regulates the hydraulicpressure applied through lines 114 and 116 to the load control cylinderassembly 102; therefore, the detrusive force applied by the piston rod108 to the tool 14 varies with the 0 command and the direction of theline of cut through the sheet material on the work surface.

it will be readily understood that with fibrous composite materials suchas boron fiber tape, the pressure signal produced by the signal shaper130 should vary cyclically with every 180 change in the direction of theline of cut. FIG. is a plot or schedule showing the input/outoutcharacteristic of the shaper 130 in one embodiment of the invention. Thepressure control signal of the shaper determined from the plot regulatesthe pressure outputs of the hydraulic valve in a proportionalrelationship and, therefore, the force applied to the tool 14 variescontinuously with the direction of the cutting path. The plot indicatesthat the maximum force occurs when 0 is equal to (n X 180) where n is aninteger and that the minimum force appears when (I is equal to (n X 180)2*: Assuming that when 0 is equal to 0, the cutting tool is translatedalong the'X axis of the cutting table 12, in other words that the X axiscorresponds with 0 commands equal to 0, 180, 360 etc., a boron fibertape should be positioned on the cutting table with the fibers arrangedparallel to the Y axis. With the shaper having the characteristicindicated in FIG. 5, the maximum detrusive force is applied to thecutting wheel 70 as the wheel moves perpendicularly across the fibersand a minimum force is applied when the cutting tool is moving parallelwith the fibers and meeting only the resistance of the relatively weakbacking material. Such modulation of the detrusive forces would permitthe cutting tool to be pressed tightly against the fibers as they arecrossed in the transverse direction in spite of any inherent resiliencyin the tool mount and the supporting surface of the table bed 34 butwould limit the detrusive force when the cutting tool met the ratherweak resistance of the backing material while being translated parallelto the fibers. An intermediate detrusive force is produced when thecutting tool traverses lines of cut running at angles intermediate theprincipal directions or axes of the boron tape.

FIG. 6 discloses the input/output characteristics of the shaper 130 inanother embodiment of the invention. In this embodiment, the detrusiveforces vary in a discontinuous or stepwise manner, the maximum forcesbeing produced along lines of cut which are close to the X axis, minimumforces being generated for lines of cut close to the Y axis andintermediate forces being produced for lines of cut which areapproximately 45 to the principal axes. I

While the present invention has been described in several preferredembodiments, it should be understood that numerous modifications andsubstitutions can be had without departing from the spirit of theinvention. Although the apparatus and the method by which the apparatusoperates has been disclosed with respect to a cutting operation forboron filament tapes, ij can be applied with equally satisfactoryresults to other cutting operations in which an anisotropic material iscut. The-particular cutting tool disclosed is a cutting wheel thatproduces a relatively constant reaction force on the support platform 62as it traverses a given direction through a sheet material; however,since a reciprocating type cutting tool also requires a greaterdetrusive force as it moves transversely across a fibrous composite, theprinciples of the present invention are also applicable to systemsreciprocating cutting tools. Accordingly, the present invention has beendescribed in several preferred embodiments by way of illustration ratherthan limitation.

We claim:

1. Apparatus for cutting pattern pieces from sheet material comprising:support means providing a work surface for holding the sheet materialfixedly in a spread condition; a cutting tool; carriage means interposedbetween the support means and the'cutting tool for moving the tool andthe support means relative to one another with the tool held in cuttingengagement with the sheet material on the work surface; movement controlmeans connected to the carriage means for controlling the relativemovement of the cutting tool and the support means to cause the cuttingtool to translate along a cutting path at the periphery of a patternpiece to be cut from the sheet material; load generating means connectedwith the carriage means and the cutting tool for applying a detrusionforce to hold the cutting tool in cutting engagement with the sheetmaterial; and load control means connected to the load generating meansto regulate in a controlled manner the generating means and therebyproduce a variable detrusion force between the tool and sheet materialas the tool translates along the periphery of the pattern piece.

2. Apparatus for cutting as defined in claim 1 wherein the load controlmeans is connected to and responsive to the movement control means forregulating the generating means and the variable detrusion force betweenthe cutting tool and the sheet material.

3. Apparatus for cutting as defined in claim 2 wherein the load controlmeans is connected to and responsive to the portion of the movementcontrol means controlling the direction of cut in the sheet material toregulate the detrusion force on the cutting tool as a function of thecutting direction.

4. Apparatus for cutting as defined in claim 1 wherein: the carriagemeans is mounted for translation parallel to the work surface of thesupport means and includes a tool mount rotatable about an axisperpendicular to the work surface and a drive motor connected in drivingrelationship to the mount and responsive to rotational commands from themovement control means for rotational positioning of the mount about theperpendicular axis; the cutting tool comprises a cutting wheel supportedin the tool mount for rolling movement about an axis parallel to thework surface; and the load control means connected to the generatingmeans is responsive to the rotational commands from the movement controlmeans for regulating the force holding the cutting wheel in engagementwith the sheet material.

5. Apparatus for cutting as defined in claim 4 wherein the cutting wheelis a carbide wheel having a sharp circumferential cutting edge.

6. Apparatus as defined in claim 4 for cutting sheet material whereinthe movement control means provides rotational commands to the drivemotor maintaining the cutting wheel substantially tangent to the cuttingpath over the sheet material.

7. Apparatus as defined in claim 6 wherein the load generating meansincludes a control load cylinder assembly connected to the cutting wheelto provide a detrusion force to the wheel and the loadcontrol meansincludes a signal shaper connected to the cylinder assembly ahdproviding a maximum detruding force from the assembly for rotationalcommands associated with a first direction and a minimum detruding forcefor rotational commands associated with a second direction oriented 90to the first direction.

8. Apparatus for cutting articles from an anisotropic sheet materialhaving different cutting characteristics along different principaldirections comprising: a work table defining a support surface forsupporting the anisotropic sheet material in a spread condition; a toolcarriage movable relative to the support surface of the work table in adirection parallel to the work surface;

a cutting tool and a cutting tool holder mounted to the tool carriageand rotatable relative to the carriage about an axis normal to the worksurface; control means connected to the tool carriage for controllingthe movement of the tool and the tool holder parallel to the supportsurface and rotationally about the normal axis to guide the cutting tooltangentially along a cutting path through the anisotropic sheetmaterial; and loading means connecting with the tool holder for urgingthe cutting tool toward the support surface with a force varying withthe direction of movement of the cutting tool through the anisotropicsheet material spread on the support surface.

9. Apparatus for cutting articles as defined in claim 8 wherein the worktable includes a bed having an exposed resilient surface defining thesupport surface of the table.

10. Apparatus for cutting articles as defined in claim 9 wherein thework table is a vacuum table having means for generating asubatmospheric pressure adjacent the support surface.

ll. Apparatus for cutting as defined in claim 8 wherein the cutting toolcomprises a wheel having a sharpened peripheral cutting edge and thewheel is supported in the tool holder about an axis parallel with thesupport surface for rotation relative to the holder.

12. Apparatus for cutting as defined in claim 8 wherein the controlmeans includes a programmed memory and a computer generatingtranslational and directional command signals for the tool and toolcarriage from information stored in the programmed memory; and theloading means is connected to the control means and is responsive to thedirectional command signals for varying the force urging the tool towardthe support surface.

13. Apparatus for cutting as defined in claim 12 wherein the loadingmeans includes a load cylinder assembly and shaping means receiving thedirectional command signals and producing stepwise varying load signalsas a function of the command signals; the load cylinder being connectedto and controlled by the shaping means to urge the cutting tool towardthe support surface with stepwise varying forces.

14. Apparatus for cutting as defined in claim 12 wherein the loadingmeans includes a loading cylinder and shaping means receiving thedirectional command signals and producing load signals varyingcontinuously as a function of the command signals; the load cylinderbeing connected to and controlled by the shaping means to urge thecutting tool toward the support surface with continuously varyingforces.

15. A method for cutting pattern pieces from a sheet materialcomprising: spreading the sheet material on a supporting surface;guiding a cutting tool over the supporting surface to cause a cuttingedge of the tool to follow in cutting engagement the periphery of apattern piece to be cut from the material; and urging the cutting tooltoward the sheet material on the supporting surface as the material iscut with a force varying with the direction of the cut over the materialat each point along the periphery of the pattern piece.

16. A method for cutting pattern pieces as defined in claim 15 includingthe step of providing a cutting tool in the form of a rotatable wheelhaving a sharp circumferential cutting edge; and wherein the step ofguiding comprises moving the wheel along the periphery of the patternpiece and maintaining the cutting wheel oriented generally tangent to oraligned with the direction of the cut at each point along the peripheryof the pattern piece. t;

17. A method for cutting as defined in claim 16 wherein the step ofurging comprises establishing a schedule of cutting forces for thevarious directions of cut through the sheet material; determining thedirection of cut at each point along the periphery of the pattern piece;and applying a force to the cutting wheel at each point along theperiphery in accordance with the direction of cut and the schedule offorces.

18. A method as defined in claim 17 wherein'the step of establishingcomprises establishing a schedule of stepwise varying cutting forces forthe various directions of cut.

19. A method as defined in claim 17 wherein the step of establishingcomprises establishing a schedule of forces varying continuously withthe various directions of cut.

20. A method of cutting an anisotropic sheet material having differentcutting resistances along different coordinate axes on a work surfaceofa cutting table comprising: positioning the anisotropic sheet materialon the work surface of the table in a spread condition; orienting thesheet material on the work surface with respect to a given referencedirection on the work surface in accordance with the anisotropiccharacteristics of the sheet material; moving a cutting tool relative tothe work surface of the table in cutting engagement with the sheetmaterial to traverse a desired line of cut; and forcing the cutting toolinto engagement with the sheet material at each point on the line of cutwith a force varying as a function of the direction of the line of cut.

21. A method of cutting an anisotropic sheet material as defined inclaim 20 wherein the step of forcing comprises forcing the tool intocutting engagement with the sheet material with a force varyingcyclically with every l80 change in direction of the line of cut.

2.2. A method of cutting an anisotropic sheet material as defined inclaim 21 wherein the step of moving comprises rolling a cutting wheelover the work surface of the table in cutting engagement with the sheetmaterial and maintaining the wheel tangent to the line of cut.

23. Apparatus for cutting a sheet material composed in part of afilamentary layer formed by a plurality of closely packed and parallelfibers comprising: a work table having a work surface on which the sheetmaterial is positioned in a spread condition for a cutting operation; atool carriage for carrying a cutting tool; controlled motor means formoving the tool carriage and the work table relative to one anotherparallel to the work surface of the table and along a controlled path; acutting tool comprised of a cutting wheel mounted freely rotatable aboutan axis parallel to the work surface; mounting means connecting the toolwith the tool carriage and including a tool holder controllablyrotatable about an axis perpendicular to the work surface for orientingthe cutting wheel relative to the direction of cut; rotary drive meansfor positioning the tool holder and the cuttingwheel rotationally aboutthe axis normal to the work surface as the toolcarriage and the worktable move relative to one another; and means for urging the cuttingwheel into cutting engagement with the sheet material on the worksurface with a force varying as a function of the angle between thefibers and the orientation of the cutting wheel.

24. Apparatus for cutting as defined in claim 23 wherein the mountingmeans includes an adjustable platform movably mounted on the toolcarriage for adjustment relative to the carriage toward and away fromthe work surface of the work table and wherein the cutting wheel andtool holder are suspended from the adjustable platform over the worksurface of the table.

25. Apparatus for cutting as defined in claim 23 wherein the cuttingwheel is a carbide cutting wheel.

1. Apparatus for cutting pattern pieces from sheet material comprising:support means providing a work surface for holding the sheet materialfixedly in a spread condition; a cutting tool; carriage means interposedbetween the support means and the cutting tool for moving the tool andthe support means relative to one another with the tool held in cuttingengagement with the sheet material on the work surface; movement controlmeans connected to the carriage means for controlling the relativemovement of the cutting tool and the support means to cause the cuttingtool to translate along a cutting path at the periphery of a patternpiece to be cut from the sheet material; load generating means connectedwith the carriage means and the cutting tool for applying a detrusionforce to hold the cutting tool in cutting engagement with the sheetmaterial; and load control means connected to the load generating meansto regulate in a controlled manner the generating means and therebyproduce a variable detrusion force between the tool and sheet materialas the tool translates along the periphery of the pattern piece. 2.Apparatus for cutting as defined in claim 1 wherein the load controlmeans is connected to and responsive to the movement control means forregulating the generating means and the variable detrusion force betweenthe cutting tool and the sheet material.
 3. Apparatus for cutting asdefined in claim 2 wherein the load control means is connected to andresponsive to the portion of the movement control means controlling thedirection of cut in the sheet material to regulate the detrusion forceon the cutting tool as a function of the cutting direction.
 4. Apparatusfor cutting as defined in claim 1 wherein: the carriage means is mountedfor translation parallel to the work surface of the support means andincludes a tool mount rotatable about an axIs perpendicular to the worksurface and a drive motor connected in driving relationship to the mountand responsive to rotational commands from the movement control meansfor rotational positioning of the mount about the perpendicular axis;the cutting tool comprises a cutting wheel supported in the tool mountfor rolling movement about an axis parallel to the work surface; and theload control means connected to the generating means is responsive tothe rotational commands from the movement control means for regulatingthe force holding the cutting wheel in engagement with the sheetmaterial.
 5. Apparatus for cutting as defined in claim 4 wherein thecutting wheel is a carbide wheel having a sharp circumferential cuttingedge.
 6. Apparatus as defined in claim 4 for cutting sheet materialwherein the movement control means provides rotational commands to thedrive motor maintaining the cutting wheel substantially tangent to thecutting path over the sheet material.
 7. Apparatus as defined in claim 6wherein the load generating means includes a control load cylinderassembly connected to the cutting wheel to provide a detrusion force tothe wheel and the load control means includes a signal shaper connectedto the cylinder assembly ahd providing a maximum detruding force fromthe assembly for rotational commands associated with a first directionand a minimum detruding force for rotational commands associated with asecond direction oriented 90* to the first direction.
 8. Apparatus forcutting articles from an anisotropic sheet material having differentcutting characteristics along different principal directions comprising:a work table defining a support surface for supporting the anisotropicsheet material in a spread condition; a tool carriage movable relativeto the support surface of the work table in a direction parallel to thework surface; a cutting tool and a cutting tool holder mounted to thetool carriage and rotatable relative to the carriage about an axisnormal to the work surface; control means connected to the tool carriagefor controlling the movement of the tool and the tool holder parallel tothe support surface and rotationally about the normal axis to guide thecutting tool tangentially along a cutting path through the anisotropicsheet material; and loading means connecting with the tool holder forurging the cutting tool toward the support surface with a force varyingwith the direction of movement of the cutting tool through theanisotropic sheet material spread on the support surface.
 9. Apparatusfor cutting articles as defined in claim 8 wherein the work tableincludes a bed having an exposed resilient surface defining the supportsurface of the table.
 10. Apparatus for cutting articles as defined inclaim 9 wherein the work table is a vacuum table having means forgenerating a subatmospheric pressure adjacent the support surface. 11.Apparatus for cutting as defined in claim 8 wherein the cutting toolcomprises a wheel having a sharpened peripheral cutting edge and thewheel is supported in the tool holder about an axis parallel with thesupport surface for rotation relative to the holder.
 12. Apparatus forcutting as defined in claim 8 wherein the control means includes aprogrammed memory and a computer generating translational anddirectional command signals for the tool and tool carriage frominformation stored in the programmed memory; and the loading means isconnected to the control means and is responsive to the directionalcommand signals for varying the force urging the tool toward the supportsurface.
 13. Apparatus for cutting as defined in claim 12 wherein theloading means includes a load cylinder assembly and shaping meansreceiving the directional command signals and producing stepwise varyingload signals as a function of the command signals; the load cylinderbeing connected to and controlled by the shaping means to urge thecutting tool toward the support surface with stepwise varying forces.14. Apparatus for cutting as defined in claim 12 wherein the loadingmeans includes a loading cylinder and shaping means receiving thedirectional command signals and producing load signals varyingcontinuously as a function of the command signals; the load cylinderbeing connected to and controlled by the shaping means to urge thecutting tool toward the support surface with continuously varyingforces.
 15. A method for cutting pattern pieces from a sheet materialcomprising: spreading the sheet material on a supporting surface;guiding a cutting tool over the supporting surface to cause a cuttingedge of the tool to follow in cutting engagement the periphery of apattern piece to be cut from the material; and urging the cutting tooltoward the sheet material on the supporting surface as the material iscut with a force varying with the direction of the cut over the materialat each point along the periphery of the pattern piece.
 16. A method forcutting pattern pieces as defined in claim 15 including the step ofproviding a cutting tool in the form of a rotatable wheel having a sharpcircumferential cutting edge; and wherein the step of guiding comprisesmoving the wheel along the periphery of the pattern piece andmaintaining the cutting wheel oriented generally tangent to or alignedwith the direction of the cut at each point along the periphery of thepattern piece.
 17. A method for cutting as defined in claim 16 whereinthe step of urging comprises establishing a schedule of cutting forcesfor the various directions of cut through the sheet material;determining the direction of cut at each point along the periphery ofthe pattern piece; and applying a force to the cutting wheel at eachpoint along the periphery in accordance with the direction of cut andthe schedule of forces.
 18. A method as defined in claim 17 wherein thestep of establishing comprises establishing a schedule of stepwisevarying cutting forces for the various directions of cut.
 19. A methodas defined in claim 17 wherein the step of establishing comprisesestablishing a schedule of forces varying continuously with the variousdirections of cut.
 20. A method of cutting an anisotropic sheet materialhaving different cutting resistances along different coordinate axes ona work surface of a cutting table comprising: positioning theanisotropic sheet material on the work surface of the table in a spreadcondition; orienting the sheet material on the work surface with respectto a given reference direction on the work surface in accordance withthe anisotropic characteristics of the sheet material; moving a cuttingtool relative to the work surface of the table in cutting engagementwith the sheet material to traverse a desired line of cut; and forcingthe cutting tool into engagement with the sheet material at each pointon the line of cut with a force varying as a function of the directionof the line of cut.
 21. A method of cutting an anisotropic sheetmaterial as defined in claim 20 wherein the step of forcing comprisesforcing the tool into cutting engagement with the sheet material with aforce varying cyclically with every 180* change in direction of the lineof cut.
 22. A method of cutting an anisotropic sheet material as definedin claim 21 wherein the step of moving comprises rolling a cutting wheelover the work surface of the table in cutting engagement with the sheetmaterial and maintaining the wheel tangent to the line of cut. 23.Apparatus for cutting a sheet material composed in part of a filamentarylayer formed by a plurality of closely packed and parallel fiberscomprising: a work table having a work surface on which the sheetmaterial is positioned in a spread condition for a cutting operation; atool carriage for carrying a cutting tool; controlled motor means formoving the tool carriage and the work table relative to one anotherparallel to the work surface of the table and along a controlled path; acutting tool comprised of a cuTting wheel mounted freely rotatable aboutan axis parallel to the work surface; mounting means connecting the toolwith the tool carriage and including a tool holder controllablyrotatable about an axis perpendicular to the work surface for orientingthe cutting wheel relative to the direction of cut; rotary drive meansfor positioning the tool holder and the cutting wheel rotationally aboutthe axis normal to the work surface as the tool carriage and the worktable move relative to one another; and means for urging the cuttingwheel into cutting engagement with the sheet material on the worksurface with a force varying as a function of the angle between thefibers and the orientation of the cutting wheel.
 24. Apparatus forcutting as defined in claim 23 wherein the mounting means includes anadjustable platform movably mounted on the tool carriage for adjustmentrelative to the carriage toward and away from the work surface of thework table and wherein the cutting wheel and tool holder are suspendedfrom the adjustable platform over the work surface of the table. 25.Apparatus for cutting as defined in claim 23 wherein the cutting wheelis a carbide cutting wheel.